The present invention relates to a method of boiling wort, whereby the wort is subjected to a pre-heating process, and the invention also relates to a device which is suitable for carrying out this method.
Wort is conventionally boiled in ventilated wort boilers. In such case, the boiling time is approximately 1 to 2 hours, and the corresponding amount of steam for the pre-heating and boiling processes is approximately 15 to 20 kg per liter of wort. Part of this extremely high amount of thermal energy can in fact be recovered in specially installed boiler-type evaporation condensers and be used to produce hot water extraneous to the process. However, the production of such hot water substantially exceeds brewery requirements and has, therefore, to be stored temporarily prior to use. It is also known to subject the wort to high-temperature boiling. In such case, the wort is continuously heated to approx. 140.degree. C. under pressure, kept at this temperature for approximately 3 minutes in a heat-retaining tube, and then released with partial evaporation. This provides a reduction in the otherwise conventional boiling time. The energy required for heating can, to a large extent, be reused regeneratively within the process, except during the discharge period.
A wort boiling process has to achieve the following objects:
On the one hand, the wort is to be "thermally stabilized", this term signifying sterilization, enzyme activation, protein coagulation, including fracture formation, and a number of other chemical reactions. In addition to the treatment temperature and the treatment duration, the movement of the wort and the formation of phase boundaries also affect the fracture formation and the subsequent beer stability.
On the other hand, volatile components which are extraneous to the beer aroma and undesirable are to be expelled during the boiling process.
During the boiling process, the wort is also concentrated by evaporation to the final concentration which is actually desired.
While the wort is being boiled, the hop substances are also removed. In such case, the extraction of the hop resins, the isomerization of the bitter acids and the subsequent decomposition and loss of individual components are significant. As well as the bitter substances, aromas are also to be removed.